The field of art to which this invention pertains is metal container coating compositions.
In the manufacture of metal containers, a thin protective synthetic resin coating is applied to the interior of the container to prevent contact of the metal surface of the can with its contents. Such coatings ideally should have good adhesion to the interior metal surface, low extractables to prevent contamination of the container contents, and a rapid cure or drying rate for economy of container manufacture. Coating compositions which have been used for a number of years include organic solvent solutions and aqueous dispersions of synthetic thermoplastic and thermosetting resins which include such compositions as vinyl resins, polybutadiene resins, epoxy resins, aminoplast resins, phenoplast resins, and oleoresinous materials.
It is particularly important that containers which are used for foods and beverages contain no contaminants which not only can affect the preservation of the foods or beverage but also can affect the taste of the stored material. Taste quality is particularly important in the storage of beverages, especially beer, wherein very small amounts, in the order of parts per million or even parts per billion, of extranious material can have a detrimental effect on taste.
In an article published in "Inclusion Compounds," Volume 3, Chapter 11, pp. 331-390, Academic Press, London, 1984, J. Szejtli discusses cyclodextrins, their chemistry, and present and potential uses..
As discussed in Food Engineering, July 1987, pp. 36-38, cyclodextrins have the ability to capture or encapsulate other molecules within their ring structures. Because of this property, cyclodextrins offer a wide range of applications across the food industry for modifying taste, texture, color and aroma of processed foods and for shielding ingredients from the degrading effect of heat, light and oxygen. One use for cyclodextrins has been the debittering of citrus fruit juices.
In "Starch/Starke 27 (1975) pp 368-376, Szejtli and Banky-Eloa discuss inclusion complexes of unsaturated fatty acids and cyclodextrins.
The stabilization of autoxidizable fatty acids with cyclodextrins is described in U.S. Pat. No. 2,827,452.
In U.S. Pat. Nos. 4,722,815 and 4,725,657, synthetic resin compositions are disclosed which are made from a synthetic resin, cyclodextrin, glycitol, and a molecular inclusion compound included in the cyclodextrin. Molecular inclusion compounds are listed as being perfumes, insecticides, mold or mildew proofing agents, anti-fungi agents and bactericides.
There is a continuing need for interior container coating compositions which prevent contaminants from mixing with the container contents and affecting the quality of said contents.